1. Description of the Prior Art
Compressed air is used in many systems for controlling machinery because compressed air is immune to electrical interference and is safe in explosive environments. Compressed air is generally used, for example, to control valves and other mechanical devices in industrial systems. When using compressed air in a system, sensors are generally provided that generate small electrical currents, in the range of 4 to 20 milliamperes, for example. These currents are used to establish a corresponding pressure of the compressed air and to provide a sufficient volume of pressurized air for accomplishing the desired mechanical task. In some systems, the conversion from electrical current to a corresponding pressure is accomplished by use of a current-to-pressure transducer that is capable of regulating the pressure of a small volume of air, wherein the volume of air is amplified by using standard pneumatic amplifiers. In the conventional current-to-pressure transducer, a nozzle is supplied that directs compressed air to the atmosphere at a rate determined by the proximity of a flapper valve to a nozzle orifice. The flapper valve is generally mounted on a rotating suspension and is rotated by magnetic forces that are generated by an electromagnet. The flapper is rotated toward the nozzle so that the air that escapes to the atmosphere is reduced. Such prior art devices are formed as delicate mechanical assemblies that require several adjustments during fabrication and are relatively expensive to produce.
It is highly desirable to employ a simple current-to-pressure transducer that lends itself to facile production at low cost without the need for individual mechanical adjustments.